The acidic proteins from the venom of Crotalus scutulatus scutulatus that are potent lethal toxins will be purified by chromatographic and electrophoretic procedures. The native toxins and the subunits derived therefrom will be characterized by chemical and physical methods. The characterization will include determinations of molecular sizes, compositions, subunit structures and spectral properties. Detailed studies of the phospholipase activity of the toxic proteins will be undertaken. The effects of the toxins and subunits on heart muscle sarcoplasmic reticulum ATPase and on the uptake of Ca 2 ion by heart muscle mitochondria and sarcoplasmic reticulum will be examined. The major protein components in the venom from Crotalus viridus concolor will be isolated and purified by chromatographic and electrophoretic techniques. The pure protein(s) will be studied in order to determine some of their chemical, physical and biochemical properties. These studies will include the determination composition, subunit structures, spectral properties and enzymatic activities.